The present invention generally relates to a parts supply method used in an electronic parts mounting machine or the like, and more particularly, to a parts supply method using a parts supply apparatus provided with a plurality of supply tables adapted to be moved independently.
The conventional parts supply method used in an electronic parts mounting machine for mounting electronic parts to a printed basic plate will be described with reference to FIG. 4, FIG. 5, FIG. 6 and FIG. 7.
FIG. 4 shows one example of an electronic parts mounting machine. The electronic parts mounting machine is composed of a mounting machine main body 1 and a parts supply apparatus 2. The mounting machine main body 1 is composed of a printed basic plate supporting apparatus 3, a rotary mounting head 4 and so on. The parts supply apparatus 2 is composed of a left supply table 6 and a right supply table 7 disposed to be freely moved on a guide rail 5.
A plurality of parts supply units 8 are set respectively on the supply tables 6 and 7, with the electronic parts being loaded on separate parts supply units 8 according to the type of part. The supply tables 6 and 7 are respectively moveable reciprocatingly on a guide rail 5 independently. The supply table 6 or 7 is moved so that the parts supply unit 8 having a required type of electronic parts loaded therein is positioned at a parts supply position 9 so as to effect a parts supply operation,
An electronic part is extracted by the rotary mounting head 4 at the parts supply position 9 and is carried to a printed basic plate supporting apparatus 3 by operation of the rotary mounting head 4. Thereafter, the electronic part is mounted onto the printed basic plate.
FIG. 5 illustrates an embodiment of the parts supply apparatus 2. A screw 10 is disposed and secured along its moving direction under the supply tables 6 and 7. A nut portion 11 to be screwed onto the screw shaft 10 and a motor 12 with the nut portion 11 being rotary-driven around the screw shaft 10 are respectively provided.
The motor 12 has a cylindrical rotor 14 disposed in a shape concentric to the screw shaft 10 within a stator 13 secured on the under face of the supply tables 6 and 7, and is rotatably supported through a bearing 15. One end portion of the rotor 14 is coupled to a nut portion 11. Accordingly, the motor 12 rotates the rotor 14 so as to rotate the nut portion 11 so that the supply tables 6 and 7 are respectively reciprocated independently along the guide rail 5.
When numerous types of electronic parts are to be used in the production of the required printed basic plates, the parts supply units 8 are distributed and loaded on both the left supply table 6 and the right supply table 7. In this case, the respective supply tables 6 and 7 must be alternately moved to the parts supply position 9 in accordance with the electronic parts to be mounted. The conventional embodiment of a parts supply method employing the alternate use of such supply tables 6 and 7 will be described next.
A first parts supply method entails moving only a supply table to be used while the other supply tables not used are stopped in respective waiting positions. FIG. 6(a) shows a condition where the left supply table 6 is used. The right supply table 7 not used moves to a waiting position 17 and is in a stop condition until such time the right supply table is used again. FIG. 6(b) shows a condition in which the right supply table 7 is selected for use. The unneeded left supply table 6 moves to a waiting position 16 and enters a stop condition. The right supply table 7 moves to a parts supply position 9.
A second parts supply method entails operating all of the supply tables 6 and 7 similarly regardless of which of the supply tables 6 and 7 is being used. FIG. 7(a) shows a condition where the left supply table 6 has been selected. FIG. 7(b) shows a condition where the right supply table 7 has been selected. In any case, both supply tables 6 and 7 behave as one supply table by moving together the same distance in the same direction while retaining the required interval therebetween.
In the conventional embodiment shown in FIG. 6, the supply table must move from the waiting position to the parts supply position upon selection of the supply table, whereby the parts supply operation is interrupted to thereby waste time and lower productivity. Generally, the waiting position is spaced a sufficient distance from the parts supply position so as to avoid interference with the movement of other supply tables, thus resulting in a large amount of wasted time each time a supply table is made to move across this distance.
In the conventional embodiment of FIG. 7, movement to and from a waiting position is not necessary upon selection of a supply table, thus resulting in a reduced consumption of time when switching over between supplying tables.
However, in contrast to the method of FIG. 6 in which one supply table is to be moved by the supply of the electronic parts, in the method of FIG. 7, two supply tables are moved simultaneously to cause mechanical vibrations during operations of long duration.
Referring again to the parts supply apparatus of FIG. 5, vibrations caused by the driving operations of the motor 12 are transmitted to the screw shaft 10. When the two supply tables 6 and 7 are simultaneously moved, the two motors 12 are simultaneously driven so as to cause large vibrations in the screw shaft 10. The vibrations of the screw shaft 10 are transmitted to the supply tables 6 and 7 mounted thereon so as to vibrate the parts supply unit 8 and the electronic parts loaded therein. As a result, the rotary mounting head 4 suffers a reduced success ratio in the engagement of the parts, which in turn deteriorates the production efficiency by increasing time consumption for the repairs and wasting electronic parts. Also, the electronic parts mounting accuracy is deteriorated due to the vibrations of the entire machine.